Chopin's entry in FED is not quite clear – the added quavers are imposed on the unchanged printed text and it is not clear whether which elements of that text are to be modified and how. We give the most natural reading of the entry, in which the added repetitions of b flat2 shorten the value of the 1st note of the bar. In that version the semiquaver b flat2 at the beginning of the second half of the bar should be struck. Another possibility is the two-part notation: 
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According to that notation, the semiquaver b flat2 remains sustained, just like in the main version.
The variant notated in FEFr is a slightly rhythmically varied version of FED, which additionally confirms its authenticity.
Repeating one note in a cantabile-type melody is among Chopin's favourite devices, cf. e.g. Nocturne in b flat Op. 9 no. 1, bar 1 and analog., Andante spianato from Op. 22, bar 19, Ballade in F minor Op. 52, bar 11 and analog.
Compare the passage in the sources »
category imprint: Differences between sources; Corrections & alterations
issues: Annotations in FED, Annotations in FEFr, Authentic post-publication changes and variants
notation: Rhythm